{"id":14300,"date":"2025-05-20T07:43:30","date_gmt":"2025-05-20T11:43:30","guid":{"rendered":"http:\/\/engineersgarag-main\/designing-1-watt-audio-power-amplifier-3-9\/"},"modified":"2025-05-21T02:13:19","modified_gmt":"2025-05-21T06:13:19","slug":"designing-1-watt-audio-power-amplifier-3-9","status":"publish","type":"post","link":"https:\/\/www.engineersgarage.com\/designing-1-watt-audio-power-amplifier-3-9\/","title":{"rendered":"Designing 1 Watt Audio Power Amplifier &#8211; 3\/9"},"content":{"rendered":"<div style=\"text-align: justify;\"><span style=\"font-size: 12px;\">In the previous tutorial, a 250 Milli Watt Audio Power Amplifier was designed using LM-386 power amplifier IC. On the basis of application, the audio amplifiers can be categorized into two classes &#8211;\u00a0<\/span><\/div>\n<div style=\"text-align: justify;\"><span style=\"font-size: 12px;\">1) Pre-Amplifier<\/span><\/div>\n<div style=\"text-align: justify;\"><span style=\"font-size: 12px;\">2) Power Amplifier<\/span><\/div>\n<div style=\"text-align: justify;\"><\/div>\n<div style=\"text-align: justify;\"><span style=\"font-size: 12px;\">The pre-amplifiers are used to level up the audio signals from a microphone or audio source to standard voltage levels while the power amplifiers are generally used at the output stage of the audio systems to boost audio signals before they are reproduced by the speakers. In this tutorial, a power amplifier with 1 Watt output power will be designed. The audio amplifier designed in this project will operate in range from 20 Hz to 20 KHz which is the same as of the audible range of frequencies by humans. The amplifier circuit will be designed to have a variable voltage gain in range from 26 dB to 46 dB.\u00a0<\/span><\/div>\n<div style=\"text-align: justify;\"><\/div>\n<div style=\"text-align: justify;\"><span style=\"font-size: 12px;\">The circuit of this amplifier uses operational amplifier as the building block. So, the LM-386 IC is the heart of the circuit. LM-386 is a low power audio power amplifier IC. The amplifier circuit will be equipped with volume control feature by using a variable resistor at the output.<\/span><\/div>\n<div style=\"text-align: justify;\"><span style=\"font-size: 12px;\">In the introductory article of this series, various design parameters of the audio amplifier circuits were discussed like Gain, Volume, Skew Rate, Linearity, Bandwidth, Clipping effect, Stability, Efficiency, SNR, Output power, THD and loop grounding. This amplifier circuit will be designed considering the following design parameters &#8211;\u00a0<\/span><\/div>\n<div style=\"text-align: justify;\"><\/div>\n<div style=\"text-align: justify;\"><span style=\"font-size: 12px;\">Gain (Voltage) &#8211; 26 dB to 46 dB<\/span><\/div>\n<div style=\"text-align: justify;\"><span style=\"font-size: 12px;\">Bandwidth &#8211; 20 Hz to 20 KHz<\/span><\/div>\n<div style=\"text-align: justify;\"><span style=\"font-size: 12px;\">Output Power &#8211; 1 W<\/span><\/div>\n<div style=\"text-align: justify;\"><\/div>\n<div style=\"text-align: justify;\"><span style=\"font-size: 12px;\">The amplifier will be designed to supply audio to a 10 Watt speaker having an impedance of 8 ohms. The circuit will have the following additional features &#8211;\u00a0<\/span><\/div>\n<div style=\"text-align: justify;\"><span style=\"font-size: 12px;\">&#8211; No Clipping Effect<\/span><\/div>\n<div style=\"text-align: justify;\"><span style=\"font-size: 12px;\">&#8211; Volume Control<\/span><\/div>\n<div style=\"text-align: justify;\"><\/div>\n<div style=\"text-align: justify;\"><span style=\"font-size: 12px;\">The designing of the circuit will be followed by testing of the circuit for the verification of the intended design factors and the observation of the output waveform on a CRO to check out for the clipping effect.\u00a0<\/span><\/div>\n<div style=\"text-align: justify;\"><\/div>\n<div style=\"text-align: justify;\"><strong><span style=\"font-size: 12px;\">Components Required &#8211;\u00a0<\/span><\/strong><\/div>\n<div style=\"text-align: justify;\"><\/div>\n<div style=\"text-align: justify;\"><img decoding=\"async\" title=\"\" src=\"https:\/\/www.engineersgarage.com\/wp-content\/uploads\/2019\/07\/Amplifier.png\" alt=\"\" \/><\/div>\n<div style=\"text-align: center;\"><span style=\"font-family: verdana,geneva,sans-serif;\"><em>Fig. 1:\u00a0List of components used for designing 1 Watt Audio Power Amplifier<\/em><\/span><\/div>\n<div style=\"text-align: justify;\"><\/div>\n<div style=\"text-align: justify;\"><strong><span style=\"font-size: 12px;\">Block Diagram &#8211;\u00a0<\/span><\/strong><\/div>\n<div style=\"text-align: justify;\"><\/div>\n<div style=\"text-align: justify;\">\n<p><img decoding=\"async\" title=\"\" src=\"https:\/\/www.engineersgarage.com\/wp-content\/uploads\/2019\/07\/Amplifier.png\" alt=\"\" \/><\/p>\n<p>&nbsp;<\/p>\n<p style=\"text-align: center;\"><span style=\"font-family: verdana,geneva,sans-serif;\"><em>Fig. 2:\u00a0Block Diagram of Audio Power Amplifier<\/em><\/span><\/p>\n<p><strong style=\"text-align: justify; font-size: 12.8px;\"><span style=\"font-size: 12px;\">Circuit Connections &#8211;\u00a0<\/span><\/strong><\/p>\n<\/div>\n<div style=\"text-align: justify;\"><\/div>\n<div style=\"text-align: justify;\"><span style=\"font-size: 12px;\">The amplifier circuit is built by assembling the following components together &#8211;\u00a0<\/span><\/div>\n<div style=\"text-align: justify;\"><\/div>\n<div style=\"text-align: justify;\"><span style=\"font-size: 12px;\">1) DC Source \u2013 A battery of 12V rating is used to power the circuit. This DC source also provides the bias voltage to the amplifier. The circuit used in this amplifier is similar to the circuit designed in the previous tutorial. Only the supply voltage is increased in this circuit.\u00a0<\/span><\/div>\n<div style=\"text-align: justify;\"><span style=\"font-size: 12px;\">\u00a0<\/span><\/div>\n<div style=\"text-align: justify;\"><span style=\"font-size: 12px;\">2) Audio Source &#8211; The audio input is provided from a smart phone. For receiving audio from the smart phone, an audio jack of 3.5 mm is plugged into the phone. The 3.5 mm audio jack has three wires &#8211; one for ground and two wires for left and right channel. As the amplifier is designed for single channel, only one of the channel wires will be connected to the amplifier as audio input. The ground wire of the jack will be connected to the common ground of the circuit.\u00a0<\/span><\/div>\n<div style=\"text-align: justify;\"><\/div>\n<div style=\"text-align: justify;\"><span style=\"font-size: 12px;\"><a href=\"https:\/\/www.engineersgarage.com\/wp-content\/uploads\/2019\/07\/3.5-mm-Audio-Jack_0.png\"><img loading=\"lazy\" decoding=\"async\" class=\"alignnone\" src=\"https:\/\/www.engineersgarage.com\/wp-content\/uploads\/2019\/07\/3.5-mm-Audio-Jack_0.png\" alt=\"3.5 mm Audio Jack\" width=\"494\" height=\"371\" \/><\/a><\/span><\/div>\n<div style=\"text-align: justify;\"><\/div>\n<div style=\"text-align: center;\"><span style=\"font-family: verdana,geneva,sans-serif;\"><em><span style=\"font-size: 12px;\">Fig. 3:\u00a0<\/span><span style=\"font-size: 12.8px;\">Image of 3.5 mm Audio Jack<\/span><\/em><\/span><\/div>\n<div style=\"text-align: center;\"><\/div>\n<div style=\"text-align: justify;\"><span style=\"font-size: 12px;\">3) LM386 Audio Power Amplifier &#8211; LM386 is a low voltage audio power amplifier IC. It operates between a voltage range of 4 V to 12 V. In this circuit, the IC is provided a bias voltage of 12 V. This IC can drive a load having impedance in range from 4 ohms to 32 ohms. As the speaker used as load at the output of the amplifier has 8 ohms impedance, the IC is suitable to drive it well. Internally, the voltage gain of the IC is set to 20 (26 dB) but it can be set between 20 (26 dB) to 200 (46 dB) by connecting a suitable combination of resistor and capacitor between its pins 1 and 8. <\/span><\/div>\n<div style=\"text-align: justify;\"><span style=\"font-size: 12px;\">The IC has 8 pins in PDIP package with the following pin configuration &#8211;\u00a0<\/span><\/div>\n<div style=\"text-align: justify;\"><\/div>\n<div style=\"text-align: justify;\"><img decoding=\"async\" title=\"\" src=\"https:\/\/www.engineersgarage.com\/wp-content\/uploads\/2019\/07\/8-Pins-PDIP-package.png\" alt=\"8-Pins-PDIP-PAckage\" \/><\/div>\n<div style=\"text-align: center;\"><span style=\"font-family: verdana,geneva,sans-serif;\"><em>Fig. 4:\u00a0Table listing Pin Configuration of LM386 Audio Power Amplifier IC<\/em><\/span><\/div>\n<div style=\"text-align: justify;\"><\/div>\n<div style=\"text-align: justify;\"><span style=\"font-size: 12px;\">The IC has the following pin diagram &#8211;\u00a0<\/span><\/div>\n<div style=\"text-align: justify;\"><\/div>\n<div style=\"text-align: justify;\"><img decoding=\"async\" title=\"\" src=\"https:\/\/www.engineersgarage.com\/wp-content\/uploads\/2019\/07\/LM-386-Pin-Diagram_0.png\" alt=\"LM-386 Pin Diagram\" \/><\/div>\n<div style=\"text-align: center;\"><span style=\"font-family: verdana,geneva,sans-serif;\"><em>Fig. 5:\u00a0Pin Diagram of LM386 Audio Power Amplifier IC<\/em><\/span><\/div>\n<div style=\"text-align: center;\"><\/div>\n<div style=\"text-align: justify;\"><\/div>\n<div style=\"text-align: justify;\"><span style=\"font-size: 12px;\">The IC has the following Internal Diagram &#8211;\u00a0<\/span><\/div>\n<div style=\"text-align: justify;\"><\/div>\n<div style=\"text-align: justify;\"><span style=\"font-size: 12px;\"><a href=\"https:\/\/www.engineersgarage.com\/wp-content\/uploads\/2019\/07\/LM-386-Internal-Circuit_0.png\"><img loading=\"lazy\" decoding=\"async\" class=\"alignnone\" src=\"https:\/\/www.engineersgarage.com\/wp-content\/uploads\/2019\/07\/LM-386-Internal-Circuit_0.png\" alt=\"LM-386 Internal Circuit\" width=\"822\" height=\"490\" \/><\/a><\/span><\/div>\n<div style=\"text-align: center;\"><span style=\"font-family: verdana,geneva,sans-serif;\"><em><span style=\"font-size: 12px;\">Fig. 6:\u00a0<\/span><span style=\"font-size: 12.8px;\">Internal Circuit Diagram of LM386 Audio Power Amplifier IC<\/span><\/em><\/span><\/div>\n<div style=\"text-align: center;\"><\/div>\n<div style=\"text-align: justify;\"><span style=\"font-size: 12px;\">Its internal circuitry can be represented by the following functional diagram &#8211;\u00a0<\/span><\/div>\n<div style=\"text-align: justify;\"><img decoding=\"async\" title=\"\" src=\"https:\/\/www.engineersgarage.com\/wp-content\/uploads\/2019\/07\/LM-386-Functional-Diagram-1.png\" alt=\"LM-386 Functional Diagram\" \/><\/div>\n<div style=\"text-align: center;\"><span style=\"font-family: verdana,geneva,sans-serif;\"><em>Fig. 7:\u00a0Internal Block Diagram of LM386 Audio Power Amplifier IC<\/em><\/span><\/div>\n<div style=\"text-align: center;\"><\/div>\n<div style=\"text-align: justify;\">\n<p><span style=\"font-size: 12px; text-align: justify;\">This IC is basically an operational amplifier whose voltage gain can be adjusted by using a proper RC circuit between its gain setting pins. If the gain setting pins are left open, the voltage gain of the amplifier is internally set to 20 (26 dB). For adjusting the gain between the desired range of 20 (26 dB) and 200 (46 dB), a variable resistor (Shown as RV2 in the circuit diagram) of 4.7 Kilo ohms and a capacitor (Shown as C1 in the circuit diagram) of 10 uF are connected between the pins 1 and 8 of the IC.\u00a0 For controlling the output volume level, a variable resistor (Shown as RV1 in the circuit diagram) is connected at the input of the non-inverting pin. This variable resistor actually changes the amplitude (input voltage level) of the input signal as amplitude defines the loudness of the audio signal.\u00a0<\/span><\/p>\n<p style=\"text-align: left;\"><span style=\"font-size: 12px; text-align: justify;\"><img decoding=\"async\" title=\"\" src=\"https:\/\/www.engineersgarage.com\/wp-content\/uploads\/2019\/07\/LM-386-IC_0.png\" alt=\"LM-386 IC\" \/><\/span><\/p>\n<p style=\"text-align: center;\"><span style=\"font-family: verdana,geneva,sans-serif;\"><em><span style=\"font-size: 12px; text-align: justify;\">Fig. 8:\u00a0<\/span><span style=\"text-align: justify; font-size: 12.8px;\">Typical Image of LM386 Audio Power Amplifier IC<\/span><\/em><\/span><\/p>\n<\/div>\n<div style=\"text-align: justify;\"><span style=\"font-size: 12px;\">The Pin 2 and 3 are the Input pins of IC. The pin 2 is the inverting input pin and it is grounded. The pin 3 is the non-inverting input pin and is used for feeding the audio signal which is to be amplified along with a 10k potentiometer and a capacitor which blocks any DC signal from the input. The pin 4 is the ground pin and is connected to the common ground. The pin 6 is the Power supply pin of IC and it is connected to 12V DC. A filter capacitor (Shown as C2 in the circuit diagram) of 100 uF is used for removing any high-frequency ripples at the input. At the pin 5 which is the output pin of the IC, a capacitor (Shown as C7 in the circuit diagram) of 1000 uF is connected to block any DC components. The DC components (as are appeared in case of clipping effect) can damage the speaker connected at the output of the circuit.\u00a0<\/span><\/div>\n<div style=\"text-align: justify;\"><\/div>\n<div style=\"text-align: justify;\"><span style=\"font-size: 12px;\">Along with this capacitor, an RC filter circuit consisting of a resistor (Shown as R1 in the circuit diagram) of 10 ohms and a capacitor (Shown as C6 in the circuit diagram) of 0.05 uF is used at the output pin. This is called a \u2018Zobel network\u2019. It ensures the impedance of speaker appears as a steady resistance for the amplifier after output. So it helps in stabilizing the frequency and oscillations at the output. If the capacitor C6 and resistor R1 are interchanged then it would be no longer a Zobel network but still, the output impedance will remain constant. The pin 7 which is the Bypass Terminal pin is grounded with a capacitor for improving the stability of the amplifier output.<\/span><\/div>\n<div style=\"text-align: justify;\"><\/div>\n<div style=\"text-align: justify;\"><span style=\"font-size: 12px;\">4) Speakers &#8211; A speaker of 10 Watt power rating\u00a0 and 8 ohms impedance is used as load at the output of the amplifier. The speaker is connected at pin 5 of the IC which is the output pin of the LM386 and the ground wire of the speaker is connected to the common ground.\u00a0<\/span><\/div>\n<div style=\"text-align: justify;\"><\/div>\n<div style=\"text-align: justify;\"><img decoding=\"async\" title=\"\" src=\"https:\/\/www.engineersgarage.com\/wp-content\/uploads\/2019\/07\/Speaker-1.png\" alt=\"10 Watt 8 Ohms Speaker\" \/><\/div>\n<div style=\"text-align: center;\"><span style=\"font-family: verdana,geneva,sans-serif;\"><em>Fig. 9:\u00a0Typical Image of 10 Watt 8 Ohms Speaker<\/em><\/span><\/div>\n<div style=\"text-align: justify;\">\n<p><span style=\"font-size: 12px; text-align: justify;\">While assembling this circuit following precautions must be taken care of &#8211;\u00a0<\/span><\/p>\n<\/div>\n<div style=\"text-align: justify;\"><\/div>\n<div style=\"text-align: justify;\"><span style=\"font-size: 12px;\">1.Always use the filtering capacitor at the input terminal of power supply to avoid the unwanted ripples.<\/span><\/div>\n<div style=\"text-align: justify;\"><\/div>\n<div style=\"text-align: justify;\"><span style=\"font-size: 12px;\">2.Use the speaker of equivalent or high power rating as amplifier output power.<\/span><\/div>\n<div style=\"text-align: justify;\"><\/div>\n<div style=\"text-align: justify;\"><span style=\"font-size: 12px;\">3.Always use a series capacitor at the output of the amplifier to block any DC component.<\/span><\/div>\n<div style=\"text-align: justify;\"><\/div>\n<div style=\"text-align: justify;\"><span style=\"font-size: 12px;\">4.Use Zobel network for frequency stability.<\/span><\/div>\n<div style=\"text-align: justify;\"><\/div>\n<div style=\"text-align: justify;\"><span style=\"font-size: 12px;\">5.Always calculate the maximum power rating of the amplifier before connecting it to the speaker. The practical value may differ from theoretical one.\u00a0<\/span><\/div>\n<div style=\"text-align: justify;\"><\/div>\n<div style=\"text-align: justify;\"><span style=\"font-size: 12px;\">6.For better stability ground the bypass pin using a capacitor.\u00a0<\/span><\/div>\n<div style=\"text-align: justify;\"><\/div>\n<div style=\"text-align: justify;\"><span style=\"font-size: 12px;\">7.Always check the power rating of LM386 IC in its datasheet, as different companies have different ratings.\u00a0<\/span><\/div>\n<div style=\"text-align: justify;\"><\/div>\n<div style=\"text-align: justify;\"><span style=\"font-size: 12px;\">8.Avoid clipping of the output signal as it may damage the speaker.\u00a0\u00a0<\/span><\/div>\n<div style=\"text-align: justify;\"><\/div>\n<div style=\"text-align: justify;\"><span style=\"font-size: 12px;\">9.Always place the components as close as possible to\u00a0 reduce the noise in\u00a0 the circuit.\u00a0<\/span><\/div>\n<div style=\"text-align: justify;\"><\/div>\n<div style=\"text-align: justify;\"><span style=\"font-size: 12px;\">10.Always follow star topology when grounding, this will keep the noise low and reduce the problem of loop grounding.\u00a0<\/span><\/div>\n<div style=\"text-align: justify;\"><\/div>\n<div style=\"text-align: justify;\"><span style=\"font-size: 12px;\"><img decoding=\"async\" title=\"\" src=\"https:\/\/www.engineersgarage.com\/wp-content\/uploads\/2019\/07\/Audio-Power-Amplifier-Circuit_4.jpg\" alt=\"1 Watt Audio Power Amplifier Circuit\" \/><\/span><\/div>\n<div style=\"text-align: justify;\"><\/div>\n<div style=\"text-align: center;\"><span style=\"font-family: verdana,geneva,sans-serif;\"><em><span style=\"font-size: 12px;\">Fig. 10:\u00a0<\/span><span style=\"font-size: 12.8px;\">Prototype of LM386 IC based 1 Watt Audio Power Amplifier<\/span><\/em><\/span><\/div>\n<div style=\"text-align: justify;\"><\/div>\n<div style=\"text-align: justify;\"><strong><span style=\"font-size: 12px;\">How the circuit works &#8211;\u00a0<\/span><\/strong><\/div>\n<div style=\"text-align: justify;\"><\/div>\n<div style=\"text-align: justify;\"><span style=\"font-size: 12px;\">The LM386 is basically an operational amplifier. The IC comes with an internal gain circuitry which has an internal resistor of 1.35 kilo ohms setting the default gain of the amplifier to 20 (26 dB). The internal resistor can be bypassed by connecting a capacitor between pins 1 and 8 of the IC. On bypassing the internal resistor, the gain is set to 200 (46 dB). The voltage gain of the amplifier can be adjusted between 20 (26 dB) and 200 (46 dB) by connecting a variable resistor in series with the bypassing capacitor.\u00a0<\/span><\/div>\n<div style=\"text-align: justify;\"><\/div>\n<div style=\"text-align: justify;\"><span style=\"font-size: 12px;\">The output power of LM386 varies as per the DC input voltage or bias voltage. According to the datasheet, the LM386N-1 has the following output power for a 9V supply voltage and 8 ohms load &#8211;\u00a0\u00a0<\/span><\/div>\n<div style=\"text-align: justify;\"><\/div>\n<div style=\"text-align: justify;\"><span style=\"font-size: 12px;\">At 9V\/8E &#8211; 500 mW (min) to 700 mW (typical)<\/span><\/div>\n<div style=\"text-align: justify;\"><\/div>\n<div style=\"text-align: justify;\"><img decoding=\"async\" title=\"\" src=\"https:\/\/www.engineersgarage.com\/wp-content\/uploads\/2019\/07\/LM-386-Electrical-Specs_0.png\" alt=\" LM-386 Electrical Characteristics \" \/><\/div>\n<div style=\"text-align: justify;\"><\/div>\n<div style=\"text-align: center;\"><span style=\"font-family: verdana,geneva,sans-serif;\"><em>Fig. 11:\u00a0Screenshot of electrical characterstics of LM386 IC from its datasheet<\/em><\/span><\/div>\n<div style=\"text-align: justify;\">\n<p><span style=\"font-size: 12px; text-align: justify;\">So, with a supply voltage set to 12V and a load of 8 ohms at the output, the\u00a0 power output of the amplifier can be approximately 1 Watt.\u00a0<\/span><\/p>\n<\/div>\n<div style=\"text-align: justify;\"><span style=\"font-size: 12px;\">Considering typical power output from the amplifier IC 700 mW (actually for 9 V) and load impedance (purely resistive and independent of frequency) being 8 ohms, the Root Mean Square Voltage at the output of the amplifier can be calculated as follow &#8211;\u00a0<\/span><\/div>\n<div style=\"text-align: justify;\"><\/div>\n<div style=\"text-align: justify;\"><span style=\"font-size: 12px;\">Po= (Vrms)2\/R<\/span><\/div>\n<div style=\"text-align: justify;\"><span style=\"font-size: 12px;\">Where,\u00a0<\/span><\/div>\n<div style=\"text-align: justify;\"><span style=\"font-size: 12px;\">Output Power, Po = 700 mW<\/span><\/div>\n<div style=\"text-align: justify;\"><span style=\"font-size: 12px;\">Load Resistance, R = 8 ohms\u00a0<\/span><\/div>\n<div style=\"text-align: justify;\"><span style=\"font-size: 12px;\">On putting the values,\u00a0<\/span><\/div>\n<div style=\"text-align: justify;\"><span style=\"font-size: 12px;\">0.7 = (Vrms)2\/8<\/span><\/div>\n<div style=\"text-align: justify;\"><span style=\"font-size: 12px;\">RMS (Root Mean Square) Voltage, Vrms = 2.37 V<\/span><\/div>\n<div style=\"text-align: justify;\"><\/div>\n<div style=\"text-align: justify;\"><span style=\"font-size: 12px;\">So, the peak to peak voltage for 700 mW power is as follow &#8211;\u00a0<\/span><\/div>\n<div style=\"text-align: justify;\"><span style=\"font-size: 12px;\">Vp-p = Vrms*(2)1\/2<\/span><\/div>\n<div style=\"text-align: justify;\"><span style=\"font-size: 12px;\">Vp-p = 2.37*1.414<\/span><\/div>\n<div style=\"text-align: justify;\"><span style=\"font-size: 12px;\">Vp-p(maximum)= 3.35 V (approx.)<\/span><\/div>\n<div style=\"text-align: justify;\"><\/div>\n<div style=\"text-align: justify;\"><span style=\"font-size: 12px;\">The maximum current delivered by the IC for 700 mW power output can be calculated as follow &#8211;\u00a0\u00a0<\/span><\/div>\n<div style=\"text-align: justify;\"><span style=\"font-size: 12px;\">Po = Vrms*Io<\/span><\/div>\n<div style=\"text-align: justify;\"><span style=\"font-size: 12px;\">0.7 = 2.37*Io<\/span><\/div>\n<div style=\"text-align: justify;\"><span style=\"font-size: 12px;\">Io = 295 mA<\/span><\/div>\n<div style=\"text-align: justify;\"><span style=\"font-size: 12px;\">Maximum Output current, Io = 295 mA (approx.)<\/span><\/div>\n<div style=\"text-align: justify;\"><\/div>\n<div style=\"text-align: justify;\"><span style=\"font-size: 12px;\">The input voltage at 26 dB gain for output Peak to Peak voltage being 3.35 V can be calculated as follow &#8211;\u00a0<\/span><\/div>\n<div style=\"text-align: justify;\"><span style=\"font-size: 12px;\">Gain = 26 db\/20<\/span><\/div>\n<div style=\"text-align: justify;\"><span style=\"font-size: 12px;\">Gain = Output voltage(peak &#8211; peak) \/ Input voltage(peak-peak)<\/span><\/div>\n<div style=\"text-align: justify;\"><span style=\"font-size: 12px;\">Input voltage = 3.35\/20<\/span><\/div>\n<div style=\"text-align: justify;\"><span style=\"font-size: 12px;\">Input voltage, Vin (p-p) = 167.5 mV<\/span><\/div>\n<div style=\"text-align: justify;\"><\/div>\n<div style=\"text-align: justify;\"><span style=\"font-size: 12px;\">The input voltage at 46 dB gain for output Peak to Peak voltage being 3.35 V can be calculated as follow &#8211;\u00a0<\/span><\/div>\n<div style=\"text-align: justify;\"><span style=\"font-size: 12px;\">Gain = 46 db\/200<\/span><\/div>\n<div style=\"text-align: justify;\"><span style=\"font-size: 12px;\">Gain = Output voltage(peak &#8211; peak) \/ Input voltage(peak-peak)<\/span><\/div>\n<div style=\"text-align: justify;\"><span style=\"font-size: 12px;\">Input voltage = 3.35\/200<\/span><\/div>\n<div style=\"text-align: justify;\"><span style=\"font-size: 12px;\">Input voltage, Vin (p-p) = 16.75 mV<\/span><\/div>\n<div style=\"text-align: justify;\"><\/div>\n<div style=\"text-align: justify;\"><span style=\"font-size: 12px;\">So, on applying an input voltage in range from 16 mV to 160 mV, the LM386 providing a voltage gain between 20 (26 dB) and 200 (46 dB), the output voltage about 3.35V must be obtained. So, the amplitude of the input signal can range from 16 mV to 160 mV without clipping.\u00a0<\/span><\/div>\n<div style=\"text-align: justify;\"><span style=\"font-size: 12px;\">Considering maximum power output from the amplifier IC being 1 W and load impedance (purely resistive and independent of frequency) being 8 ohms, the Root Mean Square Voltage at the output of the amplifier can be calculated as follow &#8211;\u00a0<\/span><\/div>\n<div style=\"text-align: justify;\"><\/div>\n<div style=\"text-align: justify;\"><span style=\"font-size: 12px;\">Po= (Vrms)2\/R<\/span><\/div>\n<div style=\"text-align: justify;\"><span style=\"font-size: 12px;\">Where,\u00a0<\/span><\/div>\n<div style=\"text-align: justify;\"><span style=\"font-size: 12px;\">Output Power, Po = 1000 mW<\/span><\/div>\n<div style=\"text-align: justify;\"><span style=\"font-size: 12px;\">Load Resistance, R = 8 ohms\u00a0<\/span><\/div>\n<div style=\"text-align: justify;\"><span style=\"font-size: 12px;\">On putting the values,\u00a0<\/span><\/div>\n<div style=\"text-align: justify;\"><span style=\"font-size: 12px;\">1 = (Vrms)2\/8<\/span><\/div>\n<div style=\"text-align: justify;\"><span style=\"font-size: 12px;\">RMS (Root Mean Square) Voltage, Vrms = 2.82 V<\/span><\/div>\n<div style=\"text-align: justify;\"><\/div>\n<div style=\"text-align: justify;\"><span style=\"font-size: 12px;\">So, the peak to peak voltage for 1000 mW power is as follow &#8211;\u00a0<\/span><\/div>\n<div style=\"text-align: justify;\"><span style=\"font-size: 12px;\">Vp-p = Vrms*(2)1\/2<\/span><\/div>\n<div style=\"text-align: justify;\"><span style=\"font-size: 12px;\">Vp-p = 2.82*1.414<\/span><\/div>\n<div style=\"text-align: justify;\"><span style=\"font-size: 12px;\">Vp-p(maximum)= 4 V (approx.)<\/span><\/div>\n<div style=\"text-align: justify;\"><\/div>\n<div style=\"text-align: justify;\"><span style=\"font-size: 12px;\">The maximum current delivered by the IC for 1000 mW power output can be calculated as follow &#8211;\u00a0\u00a0<\/span><\/div>\n<div style=\"text-align: justify;\"><span style=\"font-size: 12px;\">Po = Vrms*Io<\/span><\/div>\n<div style=\"text-align: justify;\"><span style=\"font-size: 12px;\">1 = 2.82*Io<\/span><\/div>\n<div style=\"text-align: justify;\"><span style=\"font-size: 12px;\">Io = 355 mA<\/span><\/div>\n<div style=\"text-align: justify;\"><span style=\"font-size: 12px;\">Maximum Output current, Io = 355 mA (approx.)<\/span><\/div>\n<div style=\"text-align: justify;\"><\/div>\n<div style=\"text-align: justify;\"><span style=\"font-size: 12px;\">The input voltage at 26 dB gain for output Peak to Peak voltage being 4 V can be calculated as follow &#8211;\u00a0<\/span><\/div>\n<div style=\"text-align: justify;\"><span style=\"font-size: 12px;\">Gain = 26 db\/20<\/span><\/div>\n<div style=\"text-align: justify;\"><span style=\"font-size: 12px;\">Gain = Output voltage(peak &#8211; peak) \/ Input voltage(peak-peak)<\/span><\/div>\n<div style=\"text-align: justify;\"><span style=\"font-size: 12px;\">Input voltage = 4\/20<\/span><\/div>\n<div style=\"text-align: justify;\"><span style=\"font-size: 12px;\">Input voltage, Vin (p-p) = 200 mV<\/span><\/div>\n<div style=\"text-align: justify;\"><\/div>\n<div style=\"text-align: justify;\"><span style=\"font-size: 12px;\">The input voltage at 46 dB gain for output Peak to Peak voltage being 4 V can be calculated as follow &#8211;\u00a0<\/span><\/div>\n<div style=\"text-align: justify;\"><span style=\"font-size: 12px;\">Gain = 46 db\/200<\/span><\/div>\n<div style=\"text-align: justify;\"><span style=\"font-size: 12px;\">Gain = Output voltage(peak &#8211; peak) \/ Input voltage(peak-peak)<\/span><\/div>\n<div style=\"text-align: justify;\"><span style=\"font-size: 12px;\">Input voltage = 4\/200<\/span><\/div>\n<div style=\"text-align: justify;\"><span style=\"font-size: 12px;\">Input voltage, Vin (p-p) = 20 mV<\/span><\/div>\n<div style=\"text-align: justify;\"><\/div>\n<div style=\"text-align: justify;\"><span style=\"font-size: 12px;\">So, on applying an input voltage in range from 20 mV to 200 mV, the LM386 providing a voltage gain between 20 (26 dB) and 200 (46 dB), the output voltage about 4 V must be obtained. So, the amplitude of the input signal for maximum power output of the IC at 12V supply can range from 20 mV to 200 mV without clipping.\u00a0<\/span><\/div>\n<div style=\"text-align: justify;\"><\/div>\n<div style=\"text-align: justify;\"><span style=\"font-size: 12px;\">Assuming that the IC delivers minimum power as per its datasheet, the input audio signal having amplitude in range from 20 mV to 200 mV with about 10 percent tolerance can be applied at the input of the amplifier. The input signal must be amplified from 20 times to 200 times depending upon the gain set by the variable resistor at pin 8 of the IC.\u00a0<\/span><\/div>\n<div style=\"text-align: justify;\"><\/div>\n<div style=\"text-align: justify;\"><strong><span style=\"font-size: 12px;\">Testing the circuit &#8211;\u00a0<\/span><\/strong><\/div>\n<div style=\"text-align: justify;\"><\/div>\n<div style=\"text-align: justify;\"><span style=\"font-size: 12px;\">For the testing of the amplifier circuit, the function generator is used as the input source. The function generator is used to generate a sine wave of constant amplitude and frequency. Any audio signal is also basically a sine wave so a function generator can be used instead of using a microphone or actual audio source. So, the function generator can be used as input source for testing the audio amplifier circuit. During testing, at the output also, a speaker is not used as a load as the speaker is resistive as well as inductive. At different frequencies, its inductance changes which in turn changes the impedance (R and L combination) of the speaker. So, the use of a speaker as load at the output of the amplifier for deriving its specifications may give false or non-standard results. In place of speaker, a dummy load which is purely resistive is used. As resistance does not change with frequency so it can be considered a reliable load independent of the frequency of the input audio signal.\u00a0<\/span><\/div>\n<div style=\"text-align: justify;\"><\/div>\n<div style=\"text-align: justify;\"><span style=\"font-size: 12px;\">For testing of the amplifier circuit, first the input voltage is set between the applicable range between 20 mV and 200 mV. The frequency of the input signal is set to 1 KHz. Then, the output waveform is observed at CRO and the input signal is increased until the output waveform starts clipping. The Peak to Peak output voltage just before clipping is measured for circuit analysis like determining the output power and gain of the amplifier.\u00a0<\/span><\/div>\n<div style=\"text-align: justify;\"><span style=\"font-size: 12px;\">At 20 dB gain the following input and output waveforms were observed where input signal is represented by red waveform and the output signal is represented by the yellow waveform &#8211;\u00a0<\/span><\/div>\n<div style=\"text-align: justify;\"><\/div>\n<div style=\"text-align: justify;\"><img decoding=\"async\" title=\"\" src=\"https:\/\/www.engineersgarage.com\/wp-content\/uploads\/2019\/07\/LM-386-Audio-Power-Amplifier-Output_0.png\" alt=\" LM-386 Audio Power Amplifier Output Observed on CRO\" \/><\/div>\n<div style=\"text-align: justify;\"><\/div>\n<div style=\"text-align: center;\"><span style=\"font-family: verdana,geneva,sans-serif;\"><em>Fig. 12:\u00a0Image of LM386 Audio Power Amplifier Input and Output Signals observed on CRO<\/em><\/span><\/div>\n<div style=\"text-align: center;\"><\/div>\n<div style=\"text-align: justify;\"><span style=\"font-size: 12px;\">The output waveform was observed to start clipping at 4V level. However, the load impedance was practically found to be 10 ohms instead of 8 ohms. For this impedance the power drawn by the load can be calculated as follow &#8211;\u00a0<\/span><\/div>\n<div style=\"text-align: justify;\"><\/div>\n<div style=\"text-align: justify;\"><span style=\"font-size: 12px;\">\u00a0Maximum Output power, Po = V2(p-p)\/2R<\/span><\/div>\n<div style=\"text-align: justify;\"><span style=\"font-size: 12px;\">Po = (4*4)\/(2*10)<\/span><\/div>\n<div style=\"text-align: justify;\"><span style=\"font-size: 12px;\">Po = 800 mW<\/span><\/div>\n<div style=\"text-align: justify;\"><\/div>\n<div style=\"text-align: justify;\"><span style=\"font-size: 12px;\">So, with the increased impedance of the load, the output power of the amplifier was reduced to 800 mW from theoretical value of 1 W.\u00a0<\/span><\/div>\n<div style=\"text-align: justify;\"><\/div>\n<div style=\"text-align: justify;\"><span style=\"font-size: 12px;\">At 26 dB gain the following observations were taken &#8211;\u00a0<\/span><\/div>\n<div style=\"text-align: justify;\"><\/div>\n<div style=\"text-align: justify;\"><img decoding=\"async\" title=\"\" src=\"https:\/\/www.engineersgarage.com\/wp-content\/uploads\/2019\/07\/26dB.png\" alt=\"26dB\" \/><\/div>\n<div style=\"text-align: center;\"><span style=\"font-family: verdana,geneva,sans-serif;\"><em>Fig. 13:\u00a0Table listing output characterstics of 1 Watt Audio Power Amplifier at 26 dB Gain<\/em><\/span><\/div>\n<div style=\"text-align: center;\"><\/div>\n<div style=\"text-align: justify;\"><span style=\"font-size: 12px;\">At 46 dB gain the following observations were taken &#8211;\u00a0<\/span><\/div>\n<div style=\"text-align: justify;\"><\/div>\n<div style=\"text-align: justify;\"><img decoding=\"async\" title=\"\" src=\"https:\/\/www.engineersgarage.com\/wp-content\/uploads\/2019\/07\/46dB_0.png\" alt=\"46dB\" \/><\/div>\n<div style=\"text-align: center;\"><span style=\"font-family: verdana,geneva,sans-serif;\"><em>Fig. 14:\u00a0Table listing output characterstics of 1 Watt Audio Power Amplifier at 46 dB Gain<\/em><\/span><\/div>\n<div style=\"text-align: justify;\"><\/div>\n<div style=\"text-align: justify;\"><span style=\"font-size: 12px;\">So, it can be observed that if the gain of the amplifier is set to 26 dB, the input voltage or amplitude of the input signal must not exceed 200 mV and if the gain of the amplifier is set to 46 dB, the input voltage or amplitude of the input signal must not exceed 20 mV as the output voltage from the power amplifier IC starts clipping at 4 V level.\u00a0\u00a0<\/span><\/div>\n<div style=\"text-align: justify;\"><\/div>\n<div style=\"text-align: justify;\"><span style=\"font-size: 12px;\">So, in this tutorial, an audio power amplifier having\u00a0 1 W power output (practically 800 mW power output due to actual load impedance being 10 ohms) having a gain in range from 26 dB to 46 dB is built. This amplifier circuit can be used in a TV sound system, radio amplifier or in portable audio players. The amplifier circuit designed in this tutorial is simple to construct and is small in size. It has a variable gain and volume control feature.\u00a0<\/span><span style=\"font-size: 12px;\">In the next tutorial, a Bass Boost Amplifier will be designed using LM-386 IC. <\/span><\/div>\n","protected":false},"excerpt":{"rendered":"<p>In the previous tutorial, a 250 Milli Watt Audio Power Amplifier was designed using LM-386 power amplifier IC. On the basis of application, the audio amplifiers can be categorized into two classes &#8211;&nbsp;1) Pre-Amplifier2) Power Amplifier&nbsp;The pre-amplifiers are used to level up the audio signals from a microphone or audio source to standard voltage levels while the power amplifiers are generally used at the output stage of the audio systems to boost audio signals before they are reproduced by the speakers. In this tutorial, a power amplifier with 1 Watt output power will be designed. The audio amplifier designed in this project will operate in range from 20 Hz to 20 KHz which is the same as of the audible range of frequencies by humans. The amplifier circuit will be designed to have a variable voltage gain in range from 26 dB to 46 dB. <\/p>\n","protected":false},"author":343,"featured_media":63933,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"_genesis_hide_title":false,"_genesis_hide_breadcrumbs":false,"_genesis_hide_singular_image":false,"_genesis_hide_footer_widgets":false,"_genesis_custom_body_class":"","_genesis_custom_post_class":"","_genesis_layout":"","footnotes":""},"categories":[3971,9],"tags":[],"class_list":{"2":"type-post","9":"entry","10":"has-post-thumbnail"},"acf":[],"yoast_head":"<!-- This site is optimized with the Yoast SEO Premium plugin v25.2 (Yoast SEO v25.2) - https:\/\/yoast.com\/wordpress\/plugins\/seo\/ -->\n<title>Designing 1 Watt Audio Power Amplifier - 3\/9<\/title>\n<meta name=\"description\" content=\"We will design a power amplifier with 1 Watt output power and circuit uses operational amplifier LM-386 IC as the building block.\" \/>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/www.engineersgarage.com\/designing-1-watt-audio-power-amplifier-3-9\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Designing 1 Watt Audio Power Amplifier - 3\/9\" \/>\n<meta property=\"og:description\" content=\"We will design a power amplifier with 1 Watt output power and circuit uses operational amplifier LM-386 IC as the building block.\" \/>\n<meta property=\"og:url\" content=\"https:\/\/www.engineersgarage.com\/designing-1-watt-audio-power-amplifier-3-9\/\" \/>\n<meta property=\"og:site_name\" content=\"Engineers Garage\" \/>\n<meta property=\"article:publisher\" content=\"https:\/\/www.facebook.com\/engineersgarage\" \/>\n<meta property=\"og:image\" content=\"https:\/\/www.engineersgarage.com\/wp-content\/uploads\/2018\/12\/LM-386-Audio-Power-Amplifier-Output_0.png\" \/>\n\t<meta property=\"og:image:width\" content=\"757\" \/>\n\t<meta property=\"og:image:height\" content=\"479\" \/>\n\t<meta property=\"og:image:type\" content=\"image\/png\" \/>\n<meta name=\"author\" content=\"Dikhsa\" \/>\n<meta name=\"twitter:card\" content=\"summary_large_image\" \/>\n<meta name=\"twitter:creator\" content=\"@EngineersGarage\" \/>\n<meta name=\"twitter:site\" content=\"@EngineersGarage\" \/>\n<meta name=\"twitter:label1\" content=\"Written by\" \/>\n\t<meta name=\"twitter:data1\" content=\"Dikhsa\" \/>\n\t<meta name=\"twitter:label2\" content=\"Est. reading time\" \/>\n\t<meta name=\"twitter:data2\" content=\"16 minutes\" \/>\n<script type=\"application\/ld+json\" class=\"yoast-schema-graph\">{\"@context\":\"https:\/\/schema.org\",\"@graph\":[{\"@type\":\"Article\",\"@id\":\"https:\/\/www.engineersgarage.com\/designing-1-watt-audio-power-amplifier-3-9\/#article\",\"isPartOf\":{\"@id\":\"https:\/\/www.engineersgarage.com\/designing-1-watt-audio-power-amplifier-3-9\/\"},\"author\":{\"name\":\"Dikhsa\",\"@id\":\"https:\/\/www.engineersgarage.com\/#\/schema\/person\/d827ee08fe679a66d2a4b38751279747\"},\"headline\":\"Designing 1 Watt Audio Power Amplifier &#8211; 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